Computing devices in general, and mobile computing devices in particular, may enable a user to interact with the device through touch-based input. For example, some mobile computing devices may include display devices that also accept touch input, such as presence-sensitive displays and touchscreens. Users may operate these computing devices in various ways. For example, a user may operate a mobile computing device, such as a smartphone, by cradling the smartphone in the user's palm, and provide touch input using the thumb of the same hand. As another example, when using a tablet computer, a user may hold the tablet computer by placing a corner or side of the tablet computer in each hand, and provide touch input using both thumbs.